Analog Devices Inc. AD677KRZ

Overview

AD677KRZ from Analog Devices is a 16-bit, 100 kSPS autocalibrating successive-approximation ADC with on-chip sample-hold, serial output, ±5 V to ±10 V input range, and 92 dB S/(N+D) at 100 kSPS - used in precision data acquisition systems for industrial instrumentation and automated test equipment.

For engineers reviewing the AD677KRZ datasheet, AD677KRZ pinout, AD677KRZ application, or AD677KRZ equivalent, key selection considerations include its dual-chip BiMOS II/CMOS architecture, 1 MHz full-power bandwidth, ±1.5 LSB INL (K-grade), 28-lead SOIC package, and requirement for ±12 V analog / +5 V digital supplies with separate AGND/DGND.

Technical Context

The AD677KRZ implements a switched-capacitor charge-redistribution SAR architecture with on-chip microcoded controller and calibration DAC, enabling self-correction of capacitor mismatch errors without external trims. Its two-die construction separates analog signal processing (BiMOS II) from digital control (CMOS).

It uses a 17-clock-cycle conversion sequence initiated by SAMPLE high-to-low transition, outputs twos-complement serial data via SDATA/SCLK, and supports continuous conversion mode with BUSY-driven timing coordination. Calibration requires 85,532 CLK cycles and stores correction values in on-chip RAM.

Key Specifications

Pinout & Package

AD677KRZ is housed in a 28-lead plastic small-outline IC (SOIC) package with gull-wing leads, 0.050" pitch, and JEDEC MS-012AC compliance. Thermal resistance θ_JA = 110°C/W (typical).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 16-bit SAR ADC applications.

Compared with AD7606BSTZ and ADS8860IDRCT, the AD677KRZ delivers superior dc accuracy (±1.5 LSB INL) and lower THD (–95 dB) at 100 kSPS but requires three independent supplies and external reference - making it optimal for fixed-installation precision DAQ rather than portable or multi-channel systems.

Availability

AD677KRZ is available at Aetrix Electronics and suitable for industrial instrumentation, automated test equipment, and medical data acquisition requiring stable component supply, long-term calibration integrity, and proven 16-bit dc linearity.

Supply support for AD677KRZ includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Analog Devices, Inc. is a global semiconductor company specializing in high-performance analog, mixed-signal, and digital signal processing technologies for precision measurement and signal conditioning.

The AD677KRZ belongs to Analog Devices' legacy high-accuracy SAR ADC product line, designed specifically for applications demanding uncompromised dc linearity, low distortion, and autonomous calibration in industrial and scientific instrumentation.

FAQ

What is the maximum recommended clock frequency for the AD677KRZ?

The AD677KRZ specifies a minimum CLK period of 480 ns (2.08 MHz), but 580 ns (1.72 MHz) is recommended for optimal accuracy over temperature. Exceeding this frequency risks violating setup/hold times for internal logic and degrading INL or THD performance. The device requires exactly 17 CLK pulses per conversion, so maximum throughput remains fixed at 100 kSPS regardless of CLK rate within spec.

Does the AD677KRZ require an external voltage reference?

Yes, the AD677KRZ requires an external precision voltage reference applied to the VREF pin. It supports 5 V or 10 V references, setting the full-scale input range to ±VREF. No internal reference is provided. For best performance, use a low-noise, low-drift reference (e.g., ADR445) with 0.1 µF ceramic bypass placed directly at the VREF pin.

How does autocalibration work in the AD677KRZ, and how often must it be performed?

The AD677KRZ performs autocalibration by measuring capacitor mismatch errors in its charge-redistribution array using an on-chip DAC and microcontroller, then storing correction coefficients in RAM. Calibration is typically required only at power-up after supplies and VREF stabilize. If skipped, performance may degrade to ~10-bit level. The process takes 85,532 CLK cycles and is triggered by pulsing CAL high then low.

What is the purpose of the AGND SENSE pin on the AD677KRZ?

The AGND SENSE pin on the AD677KRZ provides remote Kelvin sensing of the analog ground potential at the signal source. This compensates for voltage drops across PCB traces or cables between the sensor ground and the ADC's AGND pin, eliminating offset errors in low-level bipolar measurements - especially critical for bridge-based sensors or long-distance transducer wiring.

Can the AD677KRZ operate from a single +5 V supply?

No, the AD677KRZ requires three separate supplies: +12 V (VCC), –12 V (VEE), and +5 V (VDD). These are not interchangeable or combinable. The analog section (capacitor DAC, comparator, input buffers) needs the ±12 V rails for full-scale ±10 V input range and low distortion; the digital core runs from +5 V. Attempting single-supply operation will result in functional failure or permanent damage.